The present invention relates to apparatus for generating left and right eye images for three-dimensional photography, cinematography and videography and the means of viewing those images to produce a full stereoscopic effect.
Three-dimensional photography is achieved by recording separate left and right eye images. One technique for recording the separate left and right eye images is to use separate lenses and/or optical arrangements for the separate left and right eye images and to alter the optical properties of each image, for example by using different colour filters for the left and right eye images such as blue for one eye and red for the other, and to record the optically different images together on a recording medium so as to provide a single composite image. When viewed with suitable viewing devices, for example blue/red glasses, the composite image provides a three dimensional effect. However, because opposite colour filters are used to cancel out each other so that each eye would see only the appropriate image the resultant stereoscopic image is essentially monochromatic. This is known as the anaglyph method.
A more effective method was developed whereby the two stereoscopic views are recorded as separate images in full colour. The left and right images are projected simultaneously onto a front projection screen coated with a metallic surface. The separation between the two images is accomplished by means on polarizing filters placed in the projection beam of the left and right image with polarizing axis set at 90xc2x0 to each other and therefore cancelling each other. To ensure that each eye sees only the corresponding image the stereoscopic scene is viewed through glasses with polarizing filters whose polarizing axis are set at 90xc2x0 to other. The resultant stereoscopic image is in full colour. The stereoscopic images can be recorded by various means from two cameras set side by side to a split lens system designed to record a stereoscopic pair of images side by side or one image above the other. The latter scheme is known as the xe2x80x98over-underxe2x80x99 approach.
An alternative technique has also been developed for cinematography whereby the discrete left and right eye images are recorded separately and sequentially on the image recording medium. One way of achieving this is to record the left and right images on alternate sections of the image recording medium, i.e. on alternate frames of photographic film. The images can be viewed either by simultaneously projecting both the left and right eye images through an optical arrangement that superimposes both images onto the screen or by projecting the images sequentially at double the normal frame rate. Crossed polarising filters are placed in the projected beam of the appropriate image. The images are viewed through glasses with polarising filters whose polarisation axes are at 90xc2x0 to one another corresponding to the polarisation axes of the projected images. However in the case of the xe2x80x9cover-underxe2x80x9d method, where a single projection lens and additional optical arrangements are used to project both images the projection arrangement has a detrimental effect that the optical distortions introduced by the optical elements required to image the separate left and right images, mainly spherical aberrations, tend to be exaggerated when the two images are superimposed onto each other for viewing. A perfect match between the two images is not possible because both images are part of the same image circle, i.e. the top corners of the upper image really match the bottom corners of the lower image instead of the corresponding corners.
It would therefore be advantageous to provide apparatus for recording and viewing three-dimensional images that has the advantages of the present known systems, but that mitigates the known disadvantages of these systems.
According to a first aspect of the present invention there is provided an apparatus for providing left and right eye images along the axis of a camera lens, the apparatus comprising optical means arranged to provide said left and right eye images, whereby the left and right eye images may be simultaneously recorded as a pair of head-to-head images.
It is therefore possible to provide optical apparatus that records separate left and right eye images onto a single frame of a photographic film, or other recording medium, with the left and right eye images being recorded in a head-to-head format, i.e. when the frame is viewed directly, one image appears to be upside down above the other.
Preferably, the optical means comprises first and second optical elements arranged to receive the left and right eye images respectively and a further optical element arranged to receive said left and right eye images from said first and second optical elements and to provide said left and right eye images along the axis of the camera lens. The camera lens may be of a standard focal length i.e. 50 mm for a 35 mm format.
Preferably, the apparatus includes interocular adjustment means arranged to adjust the distance between the image axes of the first and second optical elements such that they are separated by a distance substantially consistent with the interocular distance of natural eyes. The interocular adjustment may be effected by synchronously moving the first and second optical elements along their respective image axes, thus resulting in a variation in the separation between the image axes.
Preferably, the apparatus includes convergence adjustment means, wherein the convergence of the axes of the left and right eye images as received by the apparatus can be adjusted. Preferably, the convergence adjustment means comprises an adjustment mechanism for adjusting the angle at which the first and second optical elements are set in relation to each other and to said further optical element. The convergence adjustment means may comprise a rotary adjustment mechanism. Preferably, the first and second optical elements are interconnected by a mechanical linkage, wherein the first and second optical elements are constrained to being arranged at the same angle of convergence with respect to the further optical element.
Preferably, the apparatus further includes an afocal optical element arranged to provide a relatively wide angle of view of the apparatus of approximately 60xc2x0. Preferably, the afocal optical element comprises a pair of optically identical first afocal lenses or lens groups of negative optical power, each first afocal lens or lens group being located along the respective axis of the left and right eye images and in front of said first and second optical elements. The afocal optical element further comprises a second afocal lens group, of positive optical power, located along the axis of the camera lens between the camera lens and the further optical element such that both left and right eye images are incident on the second afocal lens group. Preferably, the optical members comprising the first afocal group are each placed in front of said first and second optical elements in correct optical alignment with the optical axis of the camera lens. The two members of the first afocal group join together optically to form a circlexe2x80x94an optically cohesive unit preserving the spherical properties of the system.
Preferably the front lens group comprises a pair of individual half optical elements, each half optical element being placed in front of said first and second optical elements in correct optical alignment with the optical axis of the camera lens. These two halves join together optically to form a circlexe2x80x94an optically cohesive unit preserving the spherical properties of the system.
Preferably, both members of the first afocal group are coupled to the convergence adjustment means, wherein operation of the convergence adjustment means causes adjustment of the pair of first optical elements.
Preferably, the first and second optical elements comprise plane mirrors and the further optical element comprises a triangular prism, the plane mirrors each being arranged to reflect the light rays of the left and right eye images respectively onto opposing faces of the triangular prism, the triangular prism being arranged to redirect said incident light rays the camera lens.
Additionally or alternatively, the second afocal lens group of positive power may be replaced or augmented by parabolic mirrors placed in the position and/or in place of the reflecting prism surfaces.
Preferably, the optical apparatus is arranged to be coupled to a conventional lens of a camera or other image recording or viewing device.
According to a second aspect of the present invention there is provided an integrated camera lens for imaging left and right eye images, the camera lens comprising front and rear lens groups and a further optical element located therebetween, the further optical element comprising optical means arranged to provide the left and right eye images along the axis of the camera lens, whereby the left and right eye images may be simultaneously recorded as a pair of head-to-head images.
Preferably, the camera lens includes one or more of the preferred features of the apparatus according to the first aspect of the present invention.
According to a third aspect of the present invention there is provided apparatus for use in viewing a three-dimensional image, the apparatus comprising optical means arranged to simultaneously receive left and right eye images in the format of a pair of head-to-head images and to provide a superimposed projected image comprising the left and right eye images to a viewing screen.
Preferably, the optical means comprises first and second optical elements arranged to respectively receive the left and right eye images.
Preferably, an interocular adjustment means is provided to adjust the separation of the image axes of said first and second optical elements. For projection purposes the interocular distance between the axes of the left and right images can be much greater than the interocular distance of natural eyes.
Additionally or alternatively, the apparatus also preferably includes means for adjusting the angle of incidence of said first and second optical elements to the centre axes of the respective left and right eye images, whereby the convergence of said left and right eye images is adjustable.
Preferably, the apparatus includes afocal adjustment means arranged to provide an angle of projection of said superimposed image from said apparatus of approximately 60xc2x0.
Preferably, the optical means is arranged to be coupled to the front of a projection lens. Alternatively a composite projection lens including said optical means may be coupled directly to the projector.
The apparatus may further include polarising means for polarising the left and right eye images, whereby the superimposed composite image may be viewed using corresponding polarising filters to perceive a three-dimensional image, when projected onto a suitable metallic surface.
The apparatus may further include a viewing device comprising a viewing box into which said superimposed image is provided, the viewing box having one or more reflective surfaces that are arranged to project the composite image onto a side wall of said viewing box, the viewing box further comprising a viewing window through which said projected image may be viewed. The viewing box may further include polarising means for polarising the left and right eye images.
Alternatively, an optical element may be provided on the side wall of the viewing box on which the composite image is projected, the optical element being arranged to reflect incident light rays back along their axes, whereby a three-dimensional image may be viewed without the use of polarising elements. Preferably, the optical element may comprise front-projection material. The optical element, or front projection screen, may be placed at a distance, i.e. remote from the viewing box.
A camera lens placed in the position of the viewer and aligned correctly along the corresponding axes of the projection apparatus will be able to record either the left or the right eye image reflected from the projection screen and with a 3D apparatus attached to the camera lens both stereoscopic images may be recorded simultaneously. Moreover a subject placed within the field of view of the 3D apparatus and lit appropriately will be recorded as a three-dimensional composite image, i.e. it will blend in and become a part of the projected image. This can be particularly effective when the projected image has some foreground elements as well as the distant background and the xe2x80x9csubjectxe2x80x9d is placed at middle distance. By the manipulation of the convergence points the xe2x80x9csubjectxe2x80x9d can be integrated seamlessly into the projected image.
The same viewing box can be used to view three-dimensional images recorded by means of the first or second aspects of the present invention and reproduced in the form of photographs, videos or computer images. The head-to-head image is transferred by means of an arrangement of lenses acting as a relay to apparatus as described in the first and second aspects of the present invention and projected as a composite image onto the screen. A three-dimensional video image can be viewed in real time when a device is also attached to a video camera lens.
The viewing box can also be used for direct three-dimensional viewing (a three-dimensional periscope) utilizing the relay system with a device attached at both ends, the first device acting as a taking system that creates the left and right images and the second device as a projection system that superimposes the two images onto the viewing screen inside the box.
Advantages of the apparatus and camera lens of the present invention include the single camera system, the correct interocular distance corresponding to that of the average human eyes, variable convergence control mimicking the movements of the human eyes in the horizontal plane and wide angle of view corresponding to the stereoscopic (binocular) field of view of the average human eyes.
Another advantage of the apparatus and camera lens of aspects of the present invention is that it does not compound the spherical aberrations of the recorded images, because the left and right eye images are recorded as head-to-head images, and as such are effected equally by the spherical aberrations. When the two images are superimposed for viewing the optical distortions effectively cancel one another. The quality of the perceived three-dimensional image is therefore improved.